In this study, a multi-channel beam scanning of a coherent LiDAR (light detection and ranging) system was developed using WDM (wavelength division multiplexing) to overcome the limitations of the conventional single-beam approach, particularly its lower imaging speed. The experimental setup involved adding a WDM module to a Mach-Zehnder-type fiber-based interferometer. The original beam was divided into beams with different center wavelengths using WDM. These beams are directed at the target with a 1D Galvo scanner to build the x-y image. Interference signals between sample and reference lights were analyzed by each individual channel, enabling distance calculations through a fast Fourier transform. The proposed system with multi-channel beam scanning successfully improved scanning speed and obtained 3D images.
For frequency modulated continuous wave (FMCW) light detection and ranging (LiDAR), which is long-distance 4D measurement technology, fast Fourier transform (FFT) is necessary which requires high-performance computing devices. As the measurement target moves away, the measurable distance is limited by the increased beat frequency and coherence length of the light source. In this study, time-domain coherent LiDAR system was designed using chirped fiber Bragg grating (CFBG) at the reference arm. The proposed technology can measure distance without FFT and regardless of the coherence length of the light source. We acquired distance information and 3D images of targets over 10 meters.
Coherent light detection and ranging (LiDAR) system is widely used to measure distance. Distance and velocity measurements are important in many industries, including autonomous vehicles. However, conventional coherent LiDAR systems has limitations in measuring distance and velocity due to laser coherence length and frequency ambiguity. In this study, through wavelength division multiplexing, multi-interferometer was used to overcome these limitations. To solve the frequency ambiguity in this system, a novel method of frequency decoding is utilized. By applying the frequency decoding to our system, we can address the issues associated with proposed coherent LiDAR.
Coherent ranging is widely used as an optical method to measure a distance from a very fine area to a very wide area. Since distance measurement depends on light interference, a limitation occurs in the coherence length of a laser source light. We attempted to overcome this problem by creating multiple delay lines for each wavelength using a fiber Bragg grating (FBG) reflector in the interferometer. Using the proposed method, it is possible to measure the extended longer distance by using the conventional laser with a short coherence length.
Frequency-modulated continuous wave (FMCW) light detection and ranging (LiDAR) is attractive as the next generation of LiDAR. Since FMCW LiDAR is an optical method of measuring a distance using light interference, the distance measurement range is limited according to the coherence length of laser light. For this reason, FMCW LiDAR is forced to use a special laser with a long coherence length. In this study, we propose to increase the measurable distance range through a novel frequency decoding method using a dual interferometer. Experimentally, we can increase the measurable distance over the full range of coherence length.
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